Film-Tech Forum ARCHIVE: Omnex rectifier question

This is topic Omnex rectifier question in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by David Rigby (Member # 1301) on 04-24-2005, 11:46 AM:

Anyone have an electronic copy of the tapping diagram for this thing - or alternatively can anyone tell me the apping setting for a 900W lamp (I assume this needs to be 55A or so)?

Thanks

David

Posted by Stephen Furley (Member # 1277) on 04-24-2005, 12:25 PM:

55A is a bit high for a 900W lamp; 45A would be more like it.

Posted by Peter Hall (Member # 695) on 04-24-2005, 01:20 PM:

Hi David

I hope this helps

You should have (I think) the red wire on 0 and the brown on perhaps 1

Cheers

OMNEX RECTIFIER

Wire 1 0 Low tappings
Wire 2
1 40A
1A 40A
2 45A
3 50A
4 55A
4A 55A
5 60A

Wire 1 6 HIGH TAPPINGS
Wire 2
1 55A
1A 60A
2 65A
3 70A
4 76A
4A 80A

Posted by David Rigby (Member # 1301) on 04-25-2005, 04:02 AM:

Thanks very much guys. I agree about 55 seeming a bit high BTW - 45 was my original intention but I was then advised by someone else that 55 was more like it. Seemed a bit high to me too. 45 it is!

That's exactrly the info I needed Peter - thanks...my bit of paper with the tappings on went walkies it seems.

David

Posted by Peter Hall (Member # 695) on 04-25-2005, 06:06 AM:

Hi again David -

A word of warning - these rectifiers are not bad but they need 10 mins to settle down - set the current and strike the lamp and wait ! Otherwise it waits till you have the last screw on till it changes ..

Posted by Pete Naples (Member # 761) on 04-25-2005, 03:10 PM:

Peter that's usually a sign that the capacitors are going soft. Like any high-reactance type power supply they do need a short time to stabilise (probably to do with the bulb and the transformer warming up), but it shouldn't need anything like 10 minutes, 2-3 is right.

The circuitry is very similar to the single phase Orcon rectifier (was it FXPS?, at any rate the one found in the bottom of Optimax consoles, and similar to that found in CFS consoles), and very similar to the single phase unit now made by Strong.

Posted by Peter Hall (Member # 695) on 04-26-2005, 10:36 AM:

Hi Pete

Good to hear that you are alive ! Granted, I quite like the OMNEX rectifiers - with the demise of T and R they are the only decent single phase option other than switchers. We have found current fluctuations even from new however this is not a real problem - more so the number of bloody screws and the flimsy case that you need to deal with to adjust these.

How's Scotland ? I await some public body anouncing the conversion of all cinemas there to Digital, of course in a new proprietary format incompatible with Ireland, the UK and Hollywood..

Posted by Pete Naples (Member # 761) on 04-26-2005, 10:59 AM:

The case is a constant bone of contemption, never ceases to amaze me how it manages to distort when it's inanimate on the floor!

S'funny, it's all gone quiet in Ireland, I'm back across there in a couple of weeks, was asking how the conversions were going, expecting to arrive in a land of DLPs... The tech manager of the site I'm heading to just laughed...

Posted by Kevin Orman (Member # 3076) on 04-26-2005, 12:03 PM:

Hi guys!
Well, it always seems to take about half an hour before the final operating current is reached - it always drops once the lamp and/or power supply is warm. We have found this to apply with both switched-mode power supplies and also to our T&R rectifier. Seems to drop much more with the electronic one though meaning that if you want to end up with a 'warm' operating current of say 60amps then this will need to run at 65-68 amps on a cold lamp.
Are the OMNEX ones made on a similar pattern to the old T&R's or completely different design?

Posted by Pete Naples (Member # 761) on 04-26-2005, 05:45 PM:

Completely different design Kevin, the T & R uses some kind of moving core in the transformer to control the current, similar to the 3 phase IREM. The single phase Omnex rectifier id designed and manufactured by ourselves, although the circuitry is very similar, but not identical, to the Orcon/Strong/CFS. It uses a multi tapped transformer, you select whichever tap to give you the current you require. We recomend using them to power up to 1600w bulbs, but in reality you can probably power a 2kW at 75 amps.